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23-mile long oil plume headed to Dry Tortugas

A team of dedicated South Florida researchers
from the University of Miami’s Cooperative Institute for
Marine and Atmospheric Studies (CIMAS) and the National Oceanic
and Atmospheric Administration’s Atlantic Oceanographic
and Meteorological Laboratory (NOAA/AOML) were determined to
check on whether oil was, as predicted, being pulled into the
Loop Current and carried toward the Dry Tortugas.

The University of
Miami’s 96-foot catamaran the RV/F.G. Walton
Smith had just completed a two-week National Science
Foundation (NSF) sponsored cruise sampling the deep submerged
plumes near the Deepwater Horizon well site. NOAA/AOML offered
to pay for a few additional days, but the ship which is part of
the University National Laboratory System, had to return to
Miami on its tight schedule. The best they could do was
extend the trip home by 18 hours.

Using funding provided through CIMAS, a team was rapidly
assembled that included UM and CIMAS oceanographers Tom Lee and
Nelson Melo, as well as a group of scientists led by Michelle
Wood, director of the NOAA/AOML’s Ocean Chemistry
Division. A sampling plan was pulled together using particle
trajectories calculated by the UM Rosenstiel School of Marine
& Atmospheric Science’s Coastal Shelf Modeling Group,
in combination with information provided by Roffer’s Ocean
Fishing Forecast Service (ROFFS) and remotely sensed images
from UM’s Center for Southeastern Tropical Advanced Remote
Sensing (CSTARS). Using these sophisticated tools, the
team decided that the most likely pathway for oil to reach the
Florida Keys was for it to be pulled into a counterclockwise
rotating frontal eddy in the northeast corner of the Loop
Current, and then south along the eastern frontal zone of the
Loop Current to the Dry Tortugas.

They set out, borrowing surveying equipment from NSF scientists
who were leaving the ship, including geological oceanographer
Vernon Asper of the University of Southern Mississippi and
Samantha Joye from the University of Georgia. As they
traveled into the eddy field they saw areas of sheen, but no
tar balls.

Changing course to the south, however they found an area of
strong flow convergence within a southward flowing jet that
resulted from flow being pulled into the eddy. Knowing
that this was just the type of oceanographic feature that would
concentrate any floating material, including oil, they followed
it. At about the same time a U.S. Coast Guard flight that had
been sent to visually survey the area spotted what they thought
could be an oil slick in the area and contacted the scientists
aboard the WaltonSmith to have the ship get a
closer look at the slick.

“As we approached, we found an extensive oil slick that
stretched about 20 nm (20 miles) along the southward flowing
jet which merged with the northern front of the Loop
Current. The slick was made up of tar balls shaped like
pancakes that went from the size of a dime to about 6 inches in
diameter,” said Tom Lee, UM Research Professor Emeritus
and CIMAS scientist. “The combination of models and
satellite images, along with our shipboard observations and
ROFFS daily analysis had helped us to identify and study this
previously unidentified oil plume located off Florida’s
southwest coast and heading toward the Tortugas.”

Scientists quickly set up net tows and lowered a CTD
(Conductivity, Temperature and Depth) instrument equipped with
oil sampling devices into the water, collecting samples of both
the oil and saltwater in the area. As they headed further
south they kept looking for other tendrils oil, but increased
winds made spotting tell-tale sheens more difficult. As a
result they could not confirm the exact length of this southern
arm of the oil slick, which they had previously inferred from
their data. Samples have been provided to federally
sanctioned laboratories to confirm the source of materials
gathered.

“The good news is that the various approaches we are using
to project its pathway seem to be yielding similar answers and
guiding us properly. We need to maintain our vigilance and
expand our efforts to determine the degree of risk to unique
downstream resources like the Dry Tortugas and Florida Keys
National Marine Sanctuary, which are vital natural environments
that we need to protect,” said Peter Ortner, UM Marine
Biology and Fisheries professor and director of CIMAS.
“NOAA Cooperative Institutes, like CIMAS, continue to
stand ready to assist their federal partners with the best
available science to ensure that response and restoration
resources are deployed as proactively and responsibly as
possible during this national emergency.”

Earlier this month the National Oceanic and Atmospheric
Administration (NOAA) announced its selection of UM to continue
to lead its CIMAS partnership, which has been in place since
1977 to improve our understanding of climate, hurricanes, and
marine ecosystems along the southeastern U.S. coast. The
renewed partnership allows investigators from UM and partner
institutions to receive NOAA, as well as other federal agency
support for research projects, and facilitates collaboration
with NOAA scientists at NOAA/AOML, National Hurricane Center,
Southeast Fisheries Science Center, as well as other NOAA
facilities and 18 Cooperative Institutes nationwide.